1. Field of the Invention
The present invention generally relates to techniques for using electrical signals generated by the human body as a means of control. More specifically, the present invention relates to a method and an apparatus for using electrical signals generated by single muscle contractions to control multiple aspects of a single device or multiple devices.
2. Related Art
With more than 250,000 people living with spinal cord injuries in the United States alone, there has always been strong motivation to develop systems that can improve the independence and quality of life of people with such injuries. Individuals who are paralyzed or have other conditions which cause severely impaired mobility often need power wheelchairs to move around. Currently available power wheelchairs are typically controlled by manipulating a joystick controller with one hand. However, individuals with severe spinal injuries cannot use their hands, and thus cannot use these joystick-based wheelchairs.
Several alternative techniques based on other viable body functions have been developed for controlling power wheelchairs without using the hand. These viable body functions can include, but are not limited to, head movement, voice, tongue, eye-gaze, and breathing. However, while obviating the use of a hand to control the wheelchair, systems based on these body functions can interfere with normal body functions and routine activities.
Systems based on electrical brain signals (brain-computer interfaces or “BCIs”) provide another exciting form of human-machine interface for mobility-impaired individuals. In particular, for patients without consistent command of body muscles, BCIs provide one of the only meaningful solutions for achieving control of their environment. However, surface electroencephalographic (EEG) BCIs require electrode placement over a large part of the scalp, and direct recordings from the brain cortex require an invasive surgical procedure to implant the electrodes into the cortex. Hence, for those patients with consistent control of at least some muscles, systems based on electrical brain signals may not represent a preferable mode for controlling a power wheelchair.
Alternatively, electromyographic (EMG) systems based on electrical signals generated by muscle contractions (“EMG signals” hereafter) have been used to control moving objects, such as power wheelchairs, or video-game controllers. These EMG-based systems require no surgical electrode placement, and electrodes may be placed over only a small localized area of the head. Unfortunately, current EMG-based systems use one muscle for each control channel, and hence require multiple muscles to control multiple aspects of an object, such as navigating a power wheelchair. This requirement necessitates extensive wiring on a subject, imposes requirement on the subject to simultaneously control multiple muscles, and interferes with the normal functions of these muscles.
Hence, what is needed is a method and a system for controlling multiple objects or multiple aspects of an object using EMG signals without the above-described problems.